1. Field of the Invention
The present invention relates to a drill and more particularly to a dental bur drill.
2. Description of the Prior Art
As is well known to persons skilled in the art, one of the major problems to be solved in designing a dental bur drill concerns the lubrication of the rotor shaft to which the bur is connected. In the bur drills currently used, the rotor shaft in fact rotates at a speed ranging from 200,000 to 600,000 rpm. It is therefore essential to provide the bearings with adequate lubrication, since otherwise they overheat and become unserviceable.
One method of lubrication already known provides for the spraying of nebulized oil into the interior of the bearing cage by means of a spray-cylinder, through the air supply conduit. This system requires that the dental surgeon lubricate the bearings at the start of every working day since if this is overlooked the bearings become unserviceable because each injection of lube-oil provides an autonomy of only one working day approximately.
Another known system includes a nebulizer installed upstream of the rotor which automatically sends the lubricant to the rotor bearings by means of a calibrated solenoid valve. A lubrication method of this kind has the disadvantage of being relatively costly and bulky, requiring as it does an installation separate from the bur drill.